SpO₂/FiO₂ (S/F) Ratio with estimated P/F
SpO₂/FiO₂ (S/F) ratio with an estimated P/F ratio (Rice 2007): a noninvasive surrogate for P/F that avoids an arterial gas; lower values mark ARDS-range oxygenation.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- SpO₂
- 95 %
- FiO₂
- 0.5
Result: S/F 190 (est P/F 150) — at or below 235 (≈ P/F 200): ARDS-range oxygenation.
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Bands
- S/F 315 ≈ P/F 300 (ALI); S/F 235 ≈ P/F 200 (ARDS). Reliable only when SpO₂ ≤ 97% (ceiling effect).
What you enter
- SpO₂
- FiO₂ (fraction, 0.21–1.0)
How this is calculated
- Formula
- S/F = SpO₂ / FiO₂; estimated P/F ≈ (S/F − 64) / 0.84.
Rice TW, Wheeler AP, Bernard GR, et al. Comparison of the SpO₂/FiO₂ ratio and the PaO₂/FiO₂ ratio in patients with acute lung injury or ARDS. Chest. 2007;132(2):410-417. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.